Stirrer blades are commonly used in conjunction with laboratory flasks wherein the blades have a straight or flat top edge and a rounded bottom edge that generally conforms to the inside bottom curvature of the flask. The blade is curved to more closely associate itself with the flask for stirring a material therein. Therefore, in a proper position of conventional stirring blades, the curved bottom edge is facing downwardly and generally fits the curvature of the flask with the flat edge up.
Considerable difficulties arise when installing the conventional stirring blade since the blade often becomes inverted. Should this occur, the flat edge is disposed downwardly and is therefore not oriented to properly stir material within the flask. It is necessary to disassemble the apparatus to correct this condition. This condition generally occurs as a result of the method of installing the stirrer assembly which is accomplished by turning the blade so that its long axis parallels that of the rod or shaft. Then, after installing the blade and the shaft through a narrow neck of the flask, or through a glass bearing inserted into the top opening of the neck, the blade must then be rotated through 90.degree. to the proper position. Many times the blade turns in the wrong direction thereby causing the aforesaid inversion to occur.
To enable the blade to be inserted through the narrow neck of the flask, as mentioned above, the blade must first be oriented so that its long axis is perpendicular to the neck mouth and therefore parallel to that of the rod or shaft to which it is attached. After installing the blade and shaft through the narrow neck, or after installing the upper end of the shaft through the lower end of the glass bearing following which the blade is then inserted through the narrow neck of the flask followed by the bearing, the blade must then rotate through 90.degree. to the proper position. To enable this to occur, as disclosed in U.S. Pat. No. 3,207,489, it is common practice in the industry to form the shaft or glass rod to have a laterally extending lower end portion terminating in a circular vertical flange having a diameter greater than the largest diametral opening formed in the blade. This opening is the larger part of a keyhole shaped opening in the blade which enables the blade to be assembled in relation to the shaft or rod by first inserting the upper end of the shaft through the larger diametral opening and then sliding the blade downwardly along the entire length of the shaft towards the laterally extending lower end portion or foot defining the bottom end of the shaft. There is also a projecting member on the bottom end of the shaft or foot which the slotted portion of the keyhole opening must be aligned with to enable the blade to pass over the projecting member and onto the foot into engagement with the flange. When the blade is then rotated so the keyhole shaped opening is no longer in alignment with the lower projecting member, the blade is retained on the foot by being sandwiched between the lower projecting member and the circular flange.
Therefore, one of the disadvantages of the stirrer assembly of the aforementioned U.S. Pat. No. 3,207,489 is that the blade (1) must first be mounted to the shaft by (2) passing the upper shaft end through the keyhole shaped opening and then (3) sliding the blade along the entire length of the shaft and around the lower projection so that the aforementioned (4) interlocking of the blade to the shaft can occur. This is time-consuming and sometimes cumbersome within a laboratory environment. Once the blade is mounted to the shaft in the aforementioned manner, care must then be taken to rotate the blade so that the long axis is parallel to shaft with the keyhole part of the opening facing upwardly and away from the lower projecting portion and not downwardly in alignment with that projection. Otherwise, the stirrer blade could flip off the shaft during assembly.
It is accordingly an object of the present invention to provide a stirrer assembly wherein the stirrer blade is securely mounted to the stir shaft to avoid flip-over during assembly and insertion into a flask.
Another object is to provide a stirrer blade assembly wherein the amount of tension for securing the blade to the stir shaft can be controlled.
Yet a further object is to provide a stirring blade attachment system having a new and improved stir shaft which is manufactured to permit attachment of the blade with a "TEFLON " material nut and bolt.
Still another object is to provide a stirring blade attachment system with a new and improved stir shaft which is formed without the bottom projection and which therefore presents fewer projections which are likely to come in contact with the flask and result in breakage of the projections in the flask or breakage of the flask bottoms particularly in the event that the blade has flipped off the stir shaft as occurred in the prior art.